For the following system, if you isolated y in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

4x − y = 8
2x + 3y = 9

Question

For the following system, if you isolated y in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

4x − y = 8
2x + 3y = 9

anonymous · Answer

isolating Y on the first one you get:
-y = 8 - 4x
y = -8 + 4x    ------ (equation 3)

so if you that Y is equal that. Substitute equation 3 into the second one (the y value):

2x + 3(-8 + 4x) = 9
2x -24 + 12x = 9
14x = 9 + 24
14x = 33
x = 33/14

am i right?

hero · Answer

y = 4x - 8
y = (9-2x)/3

y = y 

3(4x-8) = 9 - 2x

12x - 24 = 9 - 2x
14x = 33

x = 33/14